The present disclosure relates in general to the field of computer data storage, and more specifically, to managing access to virtual tape volumes.
Magnetic tape data storage technology has been actively utilized for computer data storage since the 1950s. Magnetic tape drives, as with other computer technology, has advanced over the intervening decades, with the storage capabilities of modern tape drives increasing exponentially. Some modern magnetic tape cartridges allow storage of multiple terabytes on a single cartridge. Storage and cost considerations have allowed physical tape drives to remain in use in modern systems despite the advent and widespread adoption of solid-state storage devices. For instance, tape libraries are maintained and used in many archival data stores. Modern systems can be configured to make use of both physical tape storage as well as solid-state storage. Indeed, some systems are configured to virtualize tape drive volumes by having data in direct access storage device (DASD) disk or solid state storage emulate physical tape volumes. Such “virtual tape” systems can present portions of a DASD disk or solid state storage component as tape libraries or tape drives for use with existing software that makes use of physical tape storage. Virtual tape records can appear to be stored entirely on tape cartridges when they are actually located in faster, hard disk storage. Virtual tape can be used, for instance, with a hierarchical storage management (HSM) system in which data is moved as it falls through various usage thresholds to slower but less costly forms of storage media, including physical tape. Virtual tape may also be used as part of a storage area network (SAN) where less-frequently used or archived data can be managed by a single virtual tape server for a number of networked computers. A virtual tape system can further offload processing involved in deciding whether data should be available in the faster disk cache or written onto a tape cartridge. The virtual tape system also can manage data so that more of the space on a tape cartridge is actually used.